Abnormal distribution of IL-6 receptor in aged MRL/lpr mice: elevated expression on B cells and absence on CD4+ cells

Abstract

A mAb against murlne IL-6 receptor (IL-6R), KMH7, was obtained by immunization of hamster with recombinant soluble murlne IL-6R. Flow cytometry analysis of IL-6R distribution on lymphocytes in BALB/c showed that IL-6R was expressed on peripheral lymph node (LN) T cells of either CD4⁺ or CD8⁺ phenotype, and Peyer's patch lgA⁺ B cells, but not on splenic B cells and thymocytes. A similar distribution was observed In 5 week old MRL/lpr and 16-week-old MRL/n mice. In contrast, in 16 week old MRL/lpr mice of both sexes, IL-6R was expressed on splenic lgM⁺ cells. Peripheral LN CD4⁺ T cells In 16 week old female MRL/lpr mice did not express IL-6R. Thymocytes in any population with a phenotype of CD4⁺ or CD8⁺, double negative, and double positive were not stained with KMH7 In both BALB/c and MRL/lpr mice. In both strains, IL-6R was induced In CD4⁺ or CD8⁺ thymocytes after 2 days of culture, suggesting that CD4⁺ thymocytes in MRL/lpr have a potential to express IL-6R. Our results suggest that overexpression of IL-6R on B cells and absence of IL-6R on peripheral CD4⁺ cells are concurrent with, or may contribute to, B cell hyperreactlvlty and T cell abnormality in this strain.